Sideslip:
Are you a memebr of the Cessna Pilots Association? This problem has been addressed in their email magazine and on their website. It's inexpensive to join and an excellent source of top information. Email me if you want details of CPA.
I have had the problem in my FR172J. It was helped by correctly positioning the drain/vent behind the port strut. A few mm height change made a real difference. Of course this may not apply to your model.